1. Field of the Invention
The present invention relates to a battery-operable printer, and more particularly, relates to a printer having a function for checking whether remaining battery capacity has a battery-capacity level sufficient to perform paper transfer operations and print operations, (Hereinbelow, the “paper” refers to paper on which printing is to be performed).
2. Description of the Related Art
In recent years, object images taken by electronic image pickup devices are displayed on a display unit and/or are printed on paper for viewing and preservation.
With technical advances toward compactness and high pixel density of electronic image pickup elements, lightweight and compact electronic image pickup devices have been developed, and are practically used. With the advent of such compact and lightweight electronic image pickup devices, demands are made for compact and lightweight portable printers for printing object images taken by the electronic image pickup devices. In particular, demands are increased for portable printers capable of printing still images of objects taken by the electronic image pickup devices on paper. A conventional example of the portable printers can be operated by two power sources, i.e., one is a commercial power source, and the other is a battery power source. The printer can therefore be driven by the battery power source to perform print operation when the printer is hand-carried.
However, when the portable printer is operated using the battery to perform printing, problem occur. In the printer, print operation may be forced to terminate because of depletion in the battery power. In addition, when printing is resumed after the battery has been replaced, problems such as deviations and the like can occur in print positions before printing terminates and after printing has resumed. To prevent the problems such a print termination and print-positional deviations, techniques have been proposed. Japanese Unexamined Patent Application Publications No. 4-200185 and No. 11-177912, each of which disclose a printer including a function of checking whether the remaining battery capacity is at a level sufficient to perform printing to produce a desired number of sheets.
Japanese Unexamined Patent Application Publication No. 4-200185 discloses a camera with a built-in printer as a battery-powered portable apparatus having a print function. Before an image captured by the camera is printed, battery-capacity checking is performed. If the battery capacity is sufficient, printing is performed. However, if the battery capacity is not sufficient, a display unit displays a warning, and processing terminates.
Japanese Unexamined Patent Application Publication No. 11-177912 discloses a technique similar to those introduced above. According to the technique, a power-source detecting circuit, a warning unit, and a print-information preserving unit are provided in a control circuit that controls a printer. When the print size and the number of sheets are specified, and a print-commencing command is input to the printer, the control circuit drives and controls the power-source detecting circuit to detect the remaining capacity of a power-source battery, and determines whether the printer is capable of performing printing meeting the input requirements for the print size and the number of sheets. If a shortage is foreseen to occur in the remaining capacity of the power-source battery which is required to perform printing meeting the input requirements, the control circuit forcibly disables the print operation and controls the warning unit to display information prompting a user to replace the power-source battery with a new one.
The above-described determination is made based on the amount of power consumption per sheet as a coefficient. The amount of power consumption is obtained by performing experiments. Based on the coefficient, the determination is made whether printing can be performed on the specified number of sheets by using the remaining capacity of the power-source battery.
As described above, in the printer disclosed in Japanese Unexamined Patent Application Publication No. 11-177912, when printing is commenced after the print requirements have been input, the remaining capacity of the power-source battery is detected. Then, the determination is made whether the power-source battery is at a level sufficient to execute printing meeting the input print requirements. If the remaining capacity of the power-source battery is not at a level sufficient to execute printing meeting the input print requirements, the print operation is forced to terminate. Concurrently, the display unit displays information prompting the user to replace the power-source battery with a new one.
The above-described printer is included in an electronic image pickup device. A new object image can be captured during a print operation of an object image captured by the electronic image pickup device. In this case, an electronic image pickup operation is performed by interrupting the print operation, and after the electronic image pickup operation has been completed, printing for the object image for which the print operation was performed partway is resumed from the position where printing stopped.
In the above-described printer, roll-shaped paper is used, and an inkjet recording method is employed. The printer includes a memory to store image data corresponding to one scanning operation according to the inkjet recording method. During a print operation, an electronic image pickup operation is performed after one scanning operation of image data recorded in the memory. After the electronic image pickup operation has been completed, printing is resumed from image data corresponding to one scanning operation that is performed subsequent to a scanning operation of a printed image. Thereby, the position where printing terminated partway and the position wherefrom printing has resumed is apparent for each print scanning operation, and no positional deviation therefore occurs. This can be achieved with a printer that employs the inkjet printing method.
However, with a printer employing a recording method, such as a dye fusion thermal transfer recording method or a dye diffusion thermal transfer recording method, a driving battery of the printer is depleted in a relatively short period. When printing is thereby terminated in print operation, a thermal-transferring inked ribbon tends to stop in a state where the ribbon is in contact with paper. When printing is resumed after the battery has been replaced with a new one, driving systems for the inked ribbon and the paper are driven to commence printing from the position where printing terminated partway. For this reason, deviations occur in the print-commencement position, and variations occur in the thermal-transfer temperature. Consequently, differences in density and coloration occur on printed portions where printing terminated partway and printing is resumed.
According to Japanese Unexamined Patent Application Publication No. 4-200185, battery-capacity checking is performed before a sheet of recording paper is transferred, but nothing is disclosed regarding a method of increasing number of sheets of the paper to as many as possible. The method is required when printing is performed on a large number of sheets of the paper.